Great time of the year and wonderful shots Harue.
Had a quick peep in Wikipedia and I'm a little wiser thanks to your header on top of the gallery.
Ume (梅) is the Japanese name for a species of Asian plum (Prunus mume, Rosaceae). The tree originates from China (where it is called méi (梅)), but has also grown in Japan and Korea (where it is called maesil 매실) since ancient times. The tree is cultivated for its fruits and flowers. Although normally called a plum, it is actually more closely related to the apricot. Another species commonly referred to as the "Japanese plum" is the sumomo.
Sakura (Japanese kanji: 桜 or 櫻; katakana: サクラ) is the Japanese name for ornamental cherry trees, Prunus serrulata, and their blossoms. Cherry fruit (known as sakuranbo) come from a different species of tree.